The proposed research is aimed at identifying lateralities of cerebral functions which are high probability component processes of general language and spatial functions and at determining how these are differentially organized in normal persons as a function of handedness, familial sinistrality, handwriting posture, and sex. The principal methodologies utilized will be reaction time to lateralized visual and auditory stimulus materials, although simple recognition accuracy procedures are also used. The experiments represent a systematic approach to the question of how general (global) differences in language and spatial task lateralities follow from the integration of component processes. The specificaton of these component lateralities and their temporal characteristics should greatly enhance our understanding of normal brain functions and resolve many of the inconsistencies in the research literature concerning global language and spatial laterality differences as functions of the four subject variables of interest. It is also likely to place greater emphasis on the integrated functioning of the two hemispheres than has been typical of "laterality research."